On a set of a place called Emerald City, you'd expect things to be green, and they were — in ways other than hue. "Disney's a very eco-friendly company," reminds Mila Kunis, who stars in "Oz the Great and Powerful" as Theodora, one of the witches. "There were multiple trash bins for recycling and for lunch, all of our takeaways were biodegradable."

Opening March 8, the 3D movie, a prequel to "The Wizard of Oz," tells the story of how the Wizard came to Oz and the people he met there before Dorothy and her friends arrived. "It's very loyal in a lot of ways to things that needed to be revisited like the Yellow Brick Road and Emerald City and witches and flying monkeys, but there are many fresh things here," says James Franco, who plays the titular Wizard, a carnival magician and charlatan on the run who flees Kansas in a hot air balloon during a tornado and winds up in Oz. There, he pretends to be the powerful savior the local folk think he is.

"He puts on this big charade, which leads to a lot of comedic situations," says Franco, who got personal prestidigitation lessons from magician Lance Burton to prepare for the role. "I got to learn quite a few pretty cool tricks.  I can't do a lot of things without Lance's help," Franco concedes, "but if the people at the Magic Castle want to invite me as a member, I'd be happy to join."

Franco was eager to re-team with Sam Raimi, who directed him in the "Spider-Man" movies, and Kunis his co-star in several projects including "Date Night" and the upcoming "The Third Person," Paul Haggis' drama featuring three interlocking love stories. Franco and Kunis play ex-husband and wife.

Kunis describes her "Oz" character as "just a normal girl that falls in love and gets a broken heart and just so happens to be a witch. She's incredibly naïve and very young and has never really truly experienced love so she doesn't have the emotional tools to deal with heartache. So she takes the easy route," which involves a physical transformation in addition to her emotional one. She had specialty makeup that took two hours to apply and another two to take off (at least at first), but says it helped her get into Theodora.

"Very rarely are you given the opportunity to have such a fantastical character. It's fun to play somebody that has no boundaries, that has no rules.  There's no book you can read on how to play a witch so you kind of just create your own version," Kunis says. And after starring in R-rated movies like "Black Swan" and "Ted," she's elated that she's finally made a kid-friendly film that one day she can show her children and grandchildren. "It's such a sweet, special world to be a part of."

Michelle Williams plays good witch Glinda, who still gets around in a soap bubble but says there's more to her version, "Somebody who has the kind of spunk and vigor of a '30s, '40s screwball romantic comedy heroine. We wanted to make a Glinda that was a little bit more human." She was drawn to the script and the fact that "its humor wasn't mean or sarcastic. It didn't feel like a movie made for adults under the subterfuge of being made for children. It really felt like something that you could wholeheartedly bring your family to without having to explain certain parts away or cringe when they do something that's like a little bit inappropriate."

Rachel Weisz, who plays Kunis' witchy sister Evanora, jumped at "the chance to get to do something fantastical and magical and not Earth-bound. It's just something really challenging and new and different," says the star of such films as "About a Boy," "Enemy at the Gates," "The Deep Blue Sea," "The Whistleblower," and "The Constant Gardener," for which she won an Oscar. "I very much liked being a bad girl. The meaner I was, the more fun I had," she admits, noting the best part of playing a witch, made possible by wires, harnesses and CGI. "It's fun to have powers like being able to fly and have lightning bolts shoot out of your fingertips," she says. "It kind of made me feel like a child again."

Get more celebrity updates and read more entertainment news.